Abstract：Chain Pillars serving longwall face is an important factor influencing the stability of the roadway surrounding rock in the fully mechanised caving longwall face. The reasonable width of the section coal pillar is proposed, combined with the theoretical analysis, numerical simulation and field measurement for the fully mechanised caving longwall face in thick seam in Jinzhuang coal mine. Results of the numerical simulation show that when the width of the section pillar increases to 24 m, there is an 8 m wide elastic zone in the coal pillar and a saddle-shaped vertical stress distribution, which shows that the coal pillar can maintain its stability. So the reasonable width of the coal pillar is 24 m, which is close to the result of theoretical calculation (23 m). The field observations also illustrate that the 30 m wide coal pillars in the first mining face is too large resulting in a waste of resources.